The present invention relates to installation structure of a lip type seal which seals a circumferential surface of a rotary shaft of various sorts of equipment.
In the prior art, as an installation structure of a lip type seal, ones as shown in FIG. 15 and FIG. 16 are known. In these figures, reference numeral 101 designates a shaft hole housing of a equipment such as a compressor of a refrigerator in an air conditioner, numeral 102 designates a rotary shaft inserted in an inner circumference of the shaft hole housing 101, and numeral 200 designates a lip type seal which is installed to a seal installation part 101a formed on the inner circumferential surface of the shaft hole housing 101 and seals the shaft circumference of the rotary shaft 102.
The lip type seal 200 shown in FIG. 15 is provided on an inner circumference of an annular casing 201 made of metal with a main seal lip 202 made of rubber material, a resin seal lip 203 made of a low friction resin material and arranged at the rear side of the main seal lip 202, and a rear surface support ring 204 made of metal and arranged further at the rear side of the resin seal lip 203. The casing 201 is tightly fitted to the seal installation part 101a of the shaft hole housing 101 through an O-ring 205 made of rubber material. The inner circumferential part of the seal lips 202, 203 curved and extending to the side of a sealed space S1 within the machine is closely contacted with the outer circumferential surface of the rotary shaft 102.
Also in the lip type seal 200 shown in FIG. 16, an outer circumferential part of a main seal lip 202 is joined integrally with a casing 201. The casing 201 is tightly fitted to an inner circumferential surface of a seal installation part 101a of a shaft hole housing 101 through a close contact seal part 206 formed in continuation with the outer circumferential part of the main seal lip 202 made of rubber material. Other parts are constituted substantially in a similar manner to FIG. 15.
In recent years, a refrigerant circulated in a refrigeration cycle of an air conditioner has been changed to freon R134a not including chrorine which destroys an ozone layer in the stratosphere. In the freon R134a, a warming coefficient of absorbing a long wave (infrared) radiation from the ground surface and bringing the greenhouse effect is large. That is, the freon R134a is a greenhouse effect gas which may bring the earth warming even if quite little amount leaks in the air. Therefore, as a refrigerant as above described, changing is being studied from R134a to CO2 (carbon dioxide) in which a warming coefficient is relatively small.
The lip type seal in the conventional structure as above described, is excellent in the gas resisting transmission property for the freon gas and exhibits a good seal performance. In CO2, however, since the transmission property for rubber material is high, when such lip type seal is used in a shaft seal device of a compressor of a refrigerator where CO2 is a refrigerant, refrigerant CO2 of high pressure compressed within the machine easily transmits the O-ring 205 or the close contact seal part 206 made of rubber material and leaks to the outside A of the machine.
An object of the present invention is to provide installation structure of a lip type seal which can exhibit a seal performance excellent for CO2.
According to one mode of the present invention, the equipment has a rotary shaft and a housing, and a lip type seal is installed between the housing and the rotary shaft. The installation structure of the lip type seal has a casing having an annular outer circumferential part, a seal lip which is held to the inside of or held integrally with the annular outer circumferential part of the casing and seals the circumferential surface of the rotary shaft, a main gasket provided between the outside of the annular outer circumferential part of the casing and the inner circumferential surface of the housing so as to prevent the leakage of CO2, and a sub-gasket provided at the downstream of CO2 which leaks from the main gasket so as to prevent CO2 from leaking to the side of the outer atmosphere. It is preferable that the sub-gasket is made of a material having a CO2 permeability coefficient smaller than that of rubber material. The sub-gasket is arranged between the annular outer circumferential part of the casing and the inner circumferential surface of the housing.
According to another mode of the present invention, the sub-gasket is small in thickness in the, direction orthogonal to the gas transmission direction in comparison with the main gasket.
It is preferable that the sub-gasket is arranged between a rear plate extending from the annular outer circumferential part of the casing toward the rotary shaft and an opposite inner surface of the housing being opposite to the rear plate. A great portion of the rear plate extends substantially in the orthogonal direction to the axial center of the rotary shaft.
The sub-gasket is a ring such as an O-ring, a square ring or a hollow metal ring.
According to the further other mode of the present invention, the sub-gasket is a rubber sheet. For example, the sub-gasket is a rubber sheet arranged in a belt-shaped groove formed in the opposite inner surface of the housing. Otherwise, the sub-gasket is a rubber sheet provided at a rear surface of the rear plate.
The main gasket is formed in continuation with the seal lip. Otherwise, the main gasket is provided separately from the seal lip.
The main gasket is an O-ring or a close contact seal part.
In the further still other mode of the present invention, the sub-gasket is a ring made of a material (for example, resin) having a CO2 transmission coefficient (CO2 leakage coefficient) smaller than that of rubber material of an O-ring being the main gasket.
Also, the sub-gasket may be that having a small CO2 transmission amount by making the thickness small in the direction orthogonal to the gas transmission direction in comparison with the main gasket (for example, that in a sheet shape).
A structure according to still another mode of the present invention is an installation structure of a lip type seal, where an outer circumferential part of a seal lip is held to or provided integrally with an annular case, and the case is tightly fitted to an inner circumferential surface of a housing of an equipment through a main gasket provided in continuation with or separately from the seal lip, and an inner circumferential part of the seal lip is closely contacted with the outer circumferential surface of a rotary shaft which is inserted in the inner circumference of the housing, characterized in that a sub-gasket made of a material having a CO2 transmission coefficient smaller than that of rubber material is interposed between the case or the rear plate provided on the case and the opposite surface of the housing.
A structure according to still another mode of the present invention is an installation structure of a lip type seal, where an outer circumferential part of a seal lip is held to or provided integrally with an annular case, and the case is tightly fitted to an inner circumferential surface of a housing of an equipment through a main gasket provided in continuation with or separately from the seal lip, and an inner circumferential part of the seal lip is closely contacted with the outer circumferential surface of a rotary shaft which is inserted in the inner circumference of the housing, characterized in that a sub-gasket having the small thickness in the direction orthogonal to the gas transmission direction in comparison with the main gasket is interposed between the case or a rear plate provided in the case and the opposite surface of the housing.
A typical example of the equipment to which the present invention is applied, is a compressor of a refrigerator. The present invention can be applied also to other equipment.
In addition, in the present specification, xe2x80x9cfront sidexe2x80x9d means the side of a sealed space, and xe2x80x9crear surfacexe2x80x9d means a surface facing the opposite side to the sealed space, and xe2x80x9crear sidexe2x80x9d means the opposite side to the sealed space.